Viral hepatitis is known to be caused by five different viruses known as hepatitis A,B,C, D and E. HAV is an RNA virus and does not lead to long-term clinical symptoms. HBV is a DNA virus. HDV is a dependent virus that is unable to infect cells in the absence of HBV. HEV is a water-borne virus. HCV was first identified and characterized as a cause of non-A, non-B hepatitis (NANBH). Houghton et al., EPO Pub. No. 388,232. This led to the disclosure of a number of general and specific polypeptides useful as immunological reagents in identifying HCV. See, e. g., Choo et al. (1989) Science, 244:359-362; Kuo et al. (1989) Science, 244:362-364; and Houghton et al. (1991) Hepatology, 14:381-388. HCV is the major cause of blood transfusion-related hepatitis.
The prototype isolate of HCV was characterized in EP Publication Nos. 318,216 and 388,232. As used herein, the term "HCV" includes newly isolated NANBH viral species. The term "HCV-1" refers to the virus described in the above-mentioned publications.
Since the initial identification of HCV, at least six different viral types have been identified and designated HCV-1 to HCV-6. Cha et al. (1992) Proc. Natl. Acad. Sci. USA, 89:7144-7148. Within these types are numerous subtypes. The type of virus with which a patient is infected may affect the clinical prognosis and also response to various treatments. Yoshioka et al. (1992) Hepatology, 16:293-299. In light of the fact that the most serious clinical outcome of HCV infection is hepatocellular carcinoma, it would be useful to be able to determine with which type or types of HCV a patient is infected.
The method currently in use to determine virus type is genotyping; that is, isolation of viral RNA and determination of the sequence of various segments by polymerase chain reaction (PCR). Not only is this method laborious and time consuming but it is not suitable for use on samples that have been stored under conditions that do not allow for preservation of RNA or samples from patients that do not have sufficient viral titer. It would be useful to have a method for typing HCV by immunoanalysis or serotyping.
The current method for screening blood and diagnosing patients is an immunoassay. The immunoassay utilizes an antigen from HCV-1 which contains a sufficient number of common epitopes to detect antibodies to other types of HCV. The immunoassay does not distinguish between infections by different types of HCV.